Osmotic Drug Delivery

As per available reports about 15 Relevant Journals, 5 Conferences, 30 Workshops are presently dedicated exclusively to Osmotic Delivery Systems and about 2,070 articles are being published on Osmotic Delivery systems.

Osmotic drug delivery system utilizes the principles of osmotic pressure for the controlled delivery of active pharmaceutical ingredient at a predetermined zero order rate. An appropriately designed osmotic drug delivery is not influenced by different physiologic factors but affected by pharmaceutical factors, which play a pivotal role in modulating the release of drug. Carriers are also used in designs to increase the effectiveness of drug delivery to the target sites of pharmacological actions. Drug Carriers can be widely used in Drug Delivery systems like Vaccine Drug Delivery, Oral Drug Delivery, Ocular Drug Delivery, BBB Drug Delivery Systems, and also in Nanosystems like Nanosomes, Micro emulsions, Liposomes.

Their rapid Development arises from the ability to overcome the drawbacks of the currently employed therapeutic drugs, which exhibit poor biopharmaceutical and pharmacokinetic properties. Nanoparticle drug carriers provide alternative formulation strategies for those molecules thus enhancing the scope for commercialization. They are potential for prolonged drug release. The conference too offers growth to expand reserves of knowledge and explore newer realms.

The present review critically discussed about the factors affecting drug release from the delivery system such as solubility, osmotic pressure, size of delivery orifice and membrane characteristics. The major arena of this review is to highlight about the different types of osmotic drug delivery systems such as implantable, single chamber, multi chamber osmotic pumps and several specialized type of osmotic pumps. Apart from that this system is a versatile technology useful for delivery of drugs with varying solubility. The additional properties of this delivery system can also exhibit pulsatile release, burst release and colon targeting of drug. Because of its versatility, this above system seems to have promising approach which can result in improved safety profile, stable drug concentrations, uniform drug effects and dosing frequency. Current review also briefly discussed about the patents related to delivery of drugs by the principle osmotic pressure. In the recent years, pharmaceutical research has led to the development of several novel drug delivery systems. The role of drug development is to take a therapeutically effective molecule with sub-optimal physicochemical and/or physiological properties and develop an optimized product that will still be therapeutically effective but with additional benefits such as

Sustained and consistent blood levels within the therapeutic window

Enhanced bioavailability

Reduced interpatient variability

Customized delivery profiles

Decreased dosing frequency

Improved patient compliance

Reduced side effects

The drug release can be modulated by different ways but the most of novel drug delivery systems are prepared using matrix, reservoir or osmotic principle. In matrix systems, the drug is embedded in a polymer matrix and the release takes place by partitioning of drug into the polymer matrix and the surrounding medium. In contrast, reservoir systems have a drug core surrounded by a rate controlling membrane. The osmotic systems utilize the principles of osmotic pressure for the delivery of drugs in both the routes oral as well as parenteral.

Osmosis

Osmosis can be defined as the net movement of water across a selectively permeable membrane driven by a difference in osmotic pressure across the membrane. It is driven by a difference in solute concentrations across the membrane that allows passage of water, but rejects most solute molecules or ions. Osmotic pressure is the pressure which, if applied to the more concentrated solution, would prevent transport of water across the semipermeable membrane.

The first osmotic effect was reported by Abbe Nollet in 1748. Later in 1877, Pfeffer performed an experiment using semi-permeable membrane to separate sugar solution from pure water. He showed that the osmotic pressure of the sugar solution is directly proportional to the solution concentration and the absolute temperature. In 1886, Vant Hoff identified an underlying proportionality between osmotic pressure, concentration and temperature. He revealed that osmotic pressure is proportional to concentration and temperature and the relationship can be described by following equation.

Π = Ø c RT

Where, p = Osmotic pressure

Π = osmotic coefficient

c = molar concentration

R = gas constant

T = Absolute temperature

Osmotic pressure is a colligative property, which depends on concentration of solute that contributes to osmotic pressure. Solutions of different concentrations having the same solute and solvent system exhibit an osmotic pressure proportional to their concentrations. Thus a constant osmotic pressure, and thereby a constant influx of water can be achieved by an osmotic delivery system that results in a constant zero order release rate of drug.

Osmotically controlled drug delivery systems:

Osmotic pressure is used as driving force for these systems to release the drug in controlled manner. Osmotic drug delivery technique is the most interesting and widely acceptable among all other technologies used for the same. Intensive research has been carried out on osmotic systems and several patents are also published. Development of osmotic drug delivery systems was pioneered by Alza and it holds major number of the patents analyzed and also markets several products based on osmotic principle. These systems can be used for both route of administration i.e. oral and parenteral. Oral osmotic systems are known as gastro intestinal therapeutic systems (GITS). Parenteral osmotic drug delivery includes implantable pumps.

Drug delivery has been the main near-term opportunity for medical nanotechnology. This market has an estimated value of $15.8 billion for 2014 and is forecast to grow to $44.5 billion by 2019, to register a significant CAGR of 23%. The drug development category, the second fastest-growing opportunity, was projected at nearly $12.6 billion for 2014 and is expected to increase to $32.2 billion by 2019 at a 20.7% CAGR.